The present invention relates to a method of splitting a log with its medullar rays so as to produce quarters that can be converted into thin-cut sections or planks through being split along the wood grain and with its medullar rays. It especially relates to such a splitting method in which the log is held by jaws that can pivot at both its ends, thus getting the axis of its core, i.e. its longitudinal gravity axis, into a horizontal position, and is then split into four, eight or twelve quarters under the action of two opposite pairs of splitting tools that can rotate when undergoing the thrust of control cylinders, whereby one pair of tools lies in a nearly vertical plane and acts upon one end of the log for its initial splitting into four, the other pair lying in a nearly horizontal plane and acting upon the other end of the log, the splitting of the latter into eight or twelve quarters being achieved through giving the plane of this pair of tools a chosen inclination, the pairs of tools being always adjusted perpendicularly to one another.
Besides, the present invention concerns a machine of splitting logs, with the medullar rays of each log in order to produce quarters that can be converted into thin-cut sections while following the wood grain of the log and without breaking or cutting its fibers.
It should be especially noted that this splitting method and this splitting machine are designed, according to the invention, to produce quarters that can be converted into thin-cut sections along the wood grain by using the splitting method and the machine its implementation for which the U.S. Pat. No. 5,090,463 has been accorded.
In the technique currently used to produce quarters from a log, the latter is split into four, six, eight or twelve quarters by means of a splitting tool that acts vertically upon the top end of a log standing upright, so that in order to produce e.g. four halves, it is necessary to first split the log into two quarters and consecutively split each half into two, which raises the number of manipulations or passages through the machine to three and thus considerable increases the working time needed for each single quarter produced. Furthermore it should be noted that in this splitting operation, which is known for its good output and the production of suitable wood quarters, it is necessary to use logs with a nearly rectilinear grain and/or a core approximately located in the central part of both ends of each log. Besides, in most cases, the splitting tool being thrust downwards in a vertical direction by a control cylinder and striking the top end of the log like an axe, it does not act like a splitter between the layers of wood fibers but its effect produces rather a splitering of the log without regard for its grain.
The U.S. Pat. No. 3,974,867 disclosed a machine of splitting logs into four quarters which uses a tool with four fixed blades that are set quadrangularly, the tool acting upon each end of the log and being fixed on a moving bearing plate driven by a double action control cylinder. In this machine, the log is first assisted by means of rest flaps operated by control cylinders, before being squeezed at both ends between central wedges borne by the tools and then split into four quarters through the fixed blades of the two tools that are driven toward one another as a consequence of their bearing plate moving under the action of their respective control cylinder. In this known machine, the blades therefore act rather like wedges that penetrate longitudinally into the fibers, breaking or cutting them; indeed, since they have a radially fixed position, the blades can follow neither the grain of the timber nor its medullar rays and the quarters thus produced are consequently unfit for the conversion of logs into thin-cut woods through splitting.
U.S. Pat. No. 4,805,676 also disclosed a machine to cut up trunks into round timbers and split these round timbers into two, three or six quarters, whereby a thrust is exerted upon their back end to drive them forward until the splitting blades of a device located upstream penetrate into their front end and split it longitudinally. Here again, this splitting device is not adapted to split the log along its grain but, as is the case with the machine disclosed by the above-mentioned U.S. Pat. No. 3,974,867, the blades act like wedges that can break or cut the wood fibers and that are not adapted to follow the wood grain or to take its medullar rays into account because of their radially fixed position.
As a consequence, the method for splitting a log into quarters according to the present invention aims at getting rid of most of the drawbacks arising from the known splitting techniques defined above and making it possible to save time in an appreciable measure and to produce wood quarters that can be converted into thin-cut sections with as little waste as possible for an economic production while producing reliable wood quarters, even when using logs with a kernel that more or less deviates from the central part between its two ends.
On the other hand, this method of splitting a log into quarters and the machine for its implementation are designed to ensure the production of wood quarters along the grain and to bring to its lowest degree the risk of breaking the fibers and/or splitering some of the fibers layers that lie between the kernel and the sapwood.